A. Technical Field
The present invention relates to a voltage converter, and more particularly, to systems, devices and methods of dynamically controlling an output of the voltage converter to rapidly transition between different power supply voltages as required in many electronic devices.
B. Background of the Invention
In most state-of-the-art electronic devices, processors are normally driven by variable power supply voltages. A voltage regulator module is oftentimes integrated to convert a high power supply voltage of +5V, +12V or more to a much lower voltage, such as +1.5V, required by many processors. Although it is fixed in some processors, this lower voltage supply is normally adjustable according to the activity level of the processors, such that power consumption may be better conserved when the activity level is low at an idle or pseudo-idle state. This is particularly important when more and more electronic devices are becoming mobile and relying on batteries to provide power to their regular operation.
The most demanding variable power supply specifications are found in central processing units (CPU) applied in a notebook, a desktop computer or a computer server. The voltage regulator module is coupled to receive voltage identification (VID) from the CPU, and thereby, continuously adjusts the power supply voltage as requested by the CPU. For instance, an eight-bit VID may be applied to the voltage regulator module for outputting a supply voltage between 0.5V and 2.5V. As the VID varies, the supply voltage has to rapidly transition to a higher or lower voltage level within the predetermined voltage range based on the new VID. For Intel microprocessors, such transitions are normally called as VID transitions, while other devices may generally refer to them as “dynamic supply voltage transition” or “supply voltage scaling.”
A switching regulator is normally applied to convert an input supply voltage of +5V, +12V or more to the target supply voltage according to a reference voltage. The switching regulator mainly relies on a switching controller to control internal switching activities of a buck or boost converter core. When the switching regulator alternates between two control states, an inductor in the converter core temporarily store power in one control state and release it in a subsequent control state, and therefore, the output supply voltage is continuously maintained by the power that is either directly provided by the input supply voltage or previously stored in the inductor. The duty cycles of these two control states are determined according to the reference voltage and the input supply voltage, and particularly, are controlled in a closed loop by the switching controller based on the specific architecture of the switching regulator. During supply voltage scaling, the duty cycles are varied to enable the supply voltage transition to a distinct voltage level.
In prior art, supply voltage scaling is oftentimes associated with a slow slew rate, a long transition time and a long settling time. The switching regulator relies on a digital-to-analog converter (DAC) to provide the reference voltage. The reference voltage is determined according to the VID which is normally communicated via a serial interface between the processors and the voltage regulator module. Although data communication and conversion via the serial interface takes a negligible period of time, the switching regulator may nevertheless be associated with such a narrow bandwidth that the transition and settling times are fundamentally limited in supply voltage scaling.
The natural bandwidth of the switching regulator may not be sufficiently wide particularly because of the use of a large LC filter and the presence of load-line impedance. As a result, the transition and settling times may fail to track the reference voltage closely or meet the timing requirements in certain applications. A need exists to dynamically control the output of the switching regulator to rapidly transition between different power supply voltages as required in many electronic devices, and particularly in many high-end electronic devices.